A major operation in mineral processing involves the separation of desirable minerals from ore bodies within which the minerals are contained. Froth flotation is a common technique employed to facilitate such separation. In froth flotation, ground ore is typically fed as an aqueous slurry to froth flotation cells. The chemistry of the slurry is adjusted such that certain minerals selectively attach to air bubbles which rise upward through the slurry and are collected in froth near the top of a flotation cell. Thereafter, minerals in the froth can be separated from different minerals in the cell.
The surfaces of specific mineral particles in aqueous suspension are treated with chemicals called flotation reagents or collectors. Flotation reagents provide the desired mineral to be floated with a water-repellent air-avid coating that will easily adhere to an air bubble, which will raise the mineral through the slurry to the surface. The minerals are trapped within froth which is generated by vigorous agitation and aeration of the slurry in the presence of a frothing agent. The valuable mineral separated and collected during the flotation process may be either the froth product or the underflow product.
Other chemical agents, such as depressants or modifiers, can also be added to the slurry to aid in mineral separation. The presence of depressants generally assists in selectivity and/or stops unwanted minerals from floating. Modifiers facilitate collection of desired minerals. Modifiers include several classes of chemicals such as activators, alkalinity regulators and dispersants. Activators are used to make a mineral surface amenable to collector coatings. Alkalinity regulators are used to control and adjust pH, an important factor in many flotation separations. Dispersants are important for control of slimes which sometimes interfere with selectivity and increase reagent consumption.
One difficulty encountered in froth flotation is the separation of a first copper-containing mineral from a second copper-containing mineral. Typically, two such minerals will collect together during traditional froth flotation. An example of such minerals are chalcocite and enargite.
Generally, a copper-containing mineral slurry is conditioned to achieve an effective pH, that is a pH that will help effectuate desired mineral separation. The slurry is subjected to a copper flotation process, using a collector and frother as required. However, when a slurry contains a first and second copper-containing minerals with similar flotation characteristics, the process is unsatisfactory due to inefficiency in achieving the desired copper-containing mineral separation. Specifically, the separation of chalcocite from enargite using a traditional flotation process is typically unsuccessful because both minerals will generally float.
Practitioners of the froth flotation art have sought to separate desired copper-containing minerals from a second similarly floatable copper-containing mineral, but have met with limited success. One method which has been employed to enhance the separation of such minerals is to grind the mineral containing ore to an extremely fine size, e.g., less than 625 mesh. In this way, particles are formed which typically have surface characteristics of a base mineral, allowing conventional flotation techniques to be utilized. However, it is relatively expensive to grind the minerals to such an extremely fine size, and the degree of separation is often times still less than desired.
As a result, it would be advantageous to have a process for efficiently and economically separating a desired copper-containing mineral from a second copper-containing mineral having similar flotability characteristics. In particular, it would be advantageous to have a froth flotation process for effectively separating chalcocite from enargite, since it is known in the art that a high grade enargite concentrate can be economically processed using a special smelting process. Likewise, a high grade chalcocite concentrate, mostly free from enargite, can also be efficiently smelted. It would also be advantageous if the process for separating copper-containing minerals could be accomplished using ordinary flotation equipment, to produce a high grade desired copper-containing mineral concentrate.